Why do Na+ ions enter the cell when voltage-gated Na+ channels are opened in neurons?
O because the Na+ concentration is much higher outside the cell than it is inside, and
the Na+ ions are attracted to the negatively charged interior
of the cell.
When voltage-gated Na+ channels are opened in neurons, it means that the membrane potential of the cell has reached a threshold level, triggering the conformational change in the channel proteins. This allows the Na+ ions to flow into the cell. The reason Na+ ions enter the cell is due to two factors:
1. Concentration Gradient: The concentration of Na+ ions is significantly higher outside the cell compared to inside. According to the principle of diffusion, particles tend to move from an area of higher concentration to an area of lower concentration until equilibrium is reached. Hence, when the voltage-gated Na+ channels open, Na+ ions move from the region of higher concentration outside the cell to the region of lower concentration inside the cell.
2. Electrostatic Attraction: The interior of the neuron is negatively charged due to the presence of various negatively charged molecules, such as proteins and nucleic acids. This negative charge attracts the positively charged Na+ ions towards the cell's interior, resulting in the entry of Na+ ions.
Combined, the higher concentration of Na+ ions outside the cell and the electrostatic attraction to the negatively charged interior result in the influx of Na+ ions when voltage-gated Na+ channels open in neurons. This influx of Na+ ions plays a crucial role in generating action potentials and transmitting electrical signals in the nervous system.